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Updated: Jun 2, 2026
Testing the Role of Multicopy Plasmids in the Evolution of Antibiotic Resistance
Published on: May 2, 2018
[CMY-2-type plasmid-mediated AmpC ß-lactamases emerging in Tucumán, Argentina]
María A Jure1, Constanza Presti, Norma M Cudmani
1Instituto de Microbiología Dr. Luis C. Verna, Cátedra de Bacteriología, Facultad de Bioquímica, Química, Farmacia y Biotecnología, Universidad Nacional de Tucumán, San Miguel de Tucumán. majure@fbqf.unt.edu.ar
Abstract:
In the last years, Enterobacteriaceae such as Klebsiella pneumoniae, Proteus mirabilis and Escherichia coli, have acquired resistance to third-generation cephalosporins (C3G) because of the presence of plasmid-mediated AmpC ß-lactamases. The aim of this work was to detect plasmid AmpC enzymes and to investigate the predominant types in our region. Between March and July 2009, 733 consecutive isolates of Enterobacteriaceae derived from hospitals and outpatient centers were studied. Susceptibility testing was performed by disk diffusion; one P. mirabilis and three E. coli strains showed resistance to cephamycins (cefoxitin) and C3G. An E-test to determine MIC and a synergy test by aminophenylboronic disks were performed. Enzymatic activity against cefoxitin was confirmed by a microbiological assay. A polymerase chain reaction (PCR) for the detection of plasmid-mediated ampC genes of different groups was performed and a 462-bp amplicon was obtained when using primers directed against the CIT group; the obtained sequences were compared to blaCMY-2 sequences, showing 100% identity. The emergence of CMY-2-type plasmid-mediated AmpC ß-lactamases indicated the importance of implementing systematic monitoring of these resistances to avoid potential clinical and epidemiological consequences.
Insights
This study detected CMY-2 type plasmid-mediated AmpC beta-lactamases in Enterobacteriaceae, highlighting the need for monitoring antimicrobial resistance to prevent clinical and epidemiological issues.
Area of Science:
- Microbiology
- Molecular Biology
- Clinical Science
Background:
- Enterobacteriaceae, including Klebsiella pneumoniae, Proteus mirabilis, and Escherichia coli, are developing resistance to third-generation cephalosporins (C3G).
- This resistance is primarily due to plasmid-mediated AmpC beta-lactamases.
- The emergence of these resistant strains poses significant clinical and epidemiological challenges.
Purpose of the Study:
- To detect and identify plasmid-mediated AmpC enzymes in Enterobacteriaceae isolates.
- To investigate the predominant types of these enzymes in the region.
- To understand the prevalence of antimicrobial resistance in local healthcare settings.
Main Methods:
- Studied 733 Enterobacteriaceae isolates from March to July 2009.
- Performed disk diffusion and E-test for antimicrobial susceptibility testing.
- Utilized polymerase chain reaction (PCR) to detect specific ampC gene groups and sequence analysis.
Main Results:
- Identified resistance to cephamycins and C3G in one P. mirabilis and three E. coli strains.
- Confirmed enzymatic activity against cefoxitin.
- PCR detected a 462-bp amplicon against the CIT group, with 100% sequence identity to blaCMY-2.
Conclusions:
- CMY-2 type plasmid-mediated AmpC beta-lactamases are emerging in Enterobacteriaceae.
- Systematic monitoring of these resistances is crucial.
- Proactive surveillance can help mitigate potential clinical and epidemiological consequences of antimicrobial resistance.
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